A semiconductor package comprises a metal, plastic, glass, or ceramic substrate containing one or more semiconductor electronic components such as discrete devices and integrated circuits (ICs). Discrete die regions are typically simultaneously formed on a silicon wafer before being cut into individual die and then assembled in a package. Semiconductor packages protect the die from harm caused by humidity, harmful gases, and various materials used in electronic assembly. Such protection usually takes the form of an essentially airtight environmental seal to prevent moisture travel into the package, referred to herein as a hermetic seal. In the case of a solder-based seal the package is considered hermetic, and for an epoxy seal the seal is considered semi-hermetic. Therefore, a hermetic or semi-hermetic seal as used herein refers to any environmental seal of any enclosed space that houses one or more semiconductor die.
Ceramic packages are commonly used for applications requiring high performance and high reliability. Such packages can generally withstand higher temperatures as compared to traditional plastic packages, and the relatively low coefficient of thermal expansion (CTE) of ceramic materials and the cavity construction also make ceramic packages well suited for stress-sensitive devices such as MEMs sensors. A ceramic package usually includes a base, metal pin I/O contacts (terminals), and a metal or glass frit sea lid (or cover) to protect and seal off the finalized assembly. Plastic materials can also be used for semi-hermetic semiconductor packages.